For months, I've been trying to get Microsoft to answer a few questions about the Unix technologies in its intellectual property portfolio. Microsoft agreed to an interview, then backed out. So the question remains: How much Unix code does Microsoft have its hands on?

Microsoft's Unix roots go back more than 25 years. The company developed a version of Unix called Xenix in the 1980s that was widely used in its day. Separately, Microsoft acquired and distributed a software package called Windows Services for Unix that includes a Unix subsystem, hundreds of Unix utilities, and related tools. That software layer, redubbed the Subsystem for Unix-based Applications, comes included with Windows Vista Enterprise and Ultimate editions and will be bundled into the soon-to-ship Windows Server 2008. It lets you run Unix apps on Windows.

Just how much Unix code does Microsoft have in its possession, either through internal development, acquisition, or license agreements with other technology companies? And where is that code being used in Microsoft's product line or by other vendors? Microsoft won't discuss it.

Back in August, I asked Microsoft's PR agency if an interview could be arranged with Microsoft's normally talkative IP department. "I can help from the 'Unix we own and license from others' standpoint," the PR person replied. "Still trying to find a Services for Unix contact for you, but we'll get there."

But weeks passed, and that contact went quiet. In November, I tried again and was told that meetings were likely if I could wait until after Thanksgiving, but when the holiday passed, Microsoft had a change of heart. "They don't think that they can find a spokesperson for you to talk with right now," I was told by a second PR contact. What changed? "All I know is that they said they can't."

Why is Microsoft reticent on questions about Unix? My theory is that the answers to those questions might shed light on Microsoft's fear, uncertainty, and doubt campaign against Linux. For more than a year now, Microsoft officials have warned that Linux violates Microsoft patents, though without specifying which pieces of code are in violation. (That point was reiterated in my unsuccessful interview request. "Microsoft has 65 patents in Linux GUIs, 15 patents in e-mail, 42 patents in Linux Kernel, 45 patents in Open Office, and 68 other patents that read on open source," PR person No. 2 told me.)

If you follow the tangled history of Xenix, it seems that there were opportunities for parts of that operating system to make its way into other Unix variants, and potentially into Linux. Microsoft's primary partner in bringing Xenix to market was Santa Cruz Operation (the original SCO, not SCO Group, which came later). Microsoft transferred ownership of Xenix to SCO in 1987 in an agreement that gave Microsoft a 20% to 25% stake in SCO.

Microsoft later sold its shares in SCO, but did Microsoft retain any rights to Xenix? Did Microsoft patent any of the technologies in Xenix? If so, it's conceivable that Microsoft code found its way into the Unix mainstream. According to Wikipedia, SCO branched Xenix into SCO Unix, while AT&T merged Xenix with BSD, SunOS, and System V into System V Release 4 SCO Unix. SCO Group (not Santa Cruz Operation, but the former Caldera, which purchased Santa Cruz Operation's Unix assets in 2000 and then changed its name to SCO Group) has alleged that Linux developers incorporated Unix code in Linux without its permission, the gist of its lawsuit against IBM. Was any of the code in question developed by Microsoft?

Given all the twists and turns in Xenix' lineage, it leaves one wondering how many Microsoft-developed lines of Unix code are out there. And that's only half the story -- Microsoft has been securing vague rights to Unix and Linux through a series of licensing agreements going back at least five years. What, if anything, is the company doing with all those technologies?

A few examples:

*In 2003, Microsoft reached agreement to license SCO Group's Unix software. Microsoft's top lawyer Brad Smith explained it as helping to "ensure IP compliance across Microsoft solutions." At the time, I suggested in a column that Microsoft itself might have been guilty of using Unix code without all the necessary permissions, a premise Microsoft didn't deny.

*In April 2004, Microsoft and Sun Microsystems announced a "broad technology collaboration agreement" to settle long-standing legal issues. They stopped short of comprehensive patent agreement, saying only that the companies would "embark on negotiations" for a patent cross-licensing agreement.

*In November 2006, Microsoft and Novell struck a deal to improve interoperability between Windows and Novell's Suse Linux, one of the first such arrangements in which Microsoft extended patent protection to Linux users.

In the name of interoperability, Microsoft has been working the industry for more agreements of the kind with Novell. XenSource, JBoss, and SugarCRM are among those that have fallen into line. From Microsoft's point of view, questions about Unix are parlayed into a discussion of its interoperability strategy. Though Wagged was unable to get that interview I requested, they did come up with background material: 66 interoperability-related news announcements over the past 18 months.

Microsoft must stop being so secretive about its Unix holdings. Its customers and would-be IP partners should demand answers to the following questions:

What Unix code does Microsoft have in its IP portfolio?

Did Microsoft retain any rights to Xenix?

Are any of the Microsoft-patented technologies you claim are in Linux also in Unix?

Without answers to these questions, Microsoft's IP push is a one-sided publicity campaign, not the industry-wide collaborative effort it portrays. If Microsoft wants to be viewed as a good citizen in the world of standards, interoperability, patents, and intellectual property, it must come clean on the Unix question.